The preferred method of treating a great variety of hazardous and other wastes is vitrification. Materials are vitrified when they are heated to high temperatures, and if necessary combined with glass forming materials, to form the materials into a stable, leach resistant glass. Heating these materials may be performed by a variety of methods. For example, it is common to place electrodes (hereinafter joule heating electrodes) in direct contact with the waste materials, and to then pass a current through the materials. In this manner, electrical energy passing between the electrodes is converted into heat due to the resistive properties of the waste materials, thereby promoting vitrification of the waste materials. In another arrangement, a high electrical potential is generated across a pair of electrodes, or a single electrode and the waste material (hereinafter arc electrodes), to create an ionized gas, or a plasma. A plasma generated in this manner will exhibit high temperatures, ranging from approximately 3,500.degree. C. to over 10,000.degree. C. Heat from the plasma is thus radiated to the surrounding waste material.
In U.S. Pat. No. 5,666,891, titled "Arc Plasma-Melter Electro Conversion System for Waste Treatment and Resource Recovery" to Titus et al. and incorporated herein by reference, a variety of particularly useful configurations are shown wherein joule electrodes are used in systems in various combinations with arc electrodes. In these arrangements, organic compounds contained in the waste are destroyed by pyrolysis, wherein the high temperatures of the plasma break the chemical bonds of the organic molecules. By introducing steam to the process chamber, these pyrolyzed organic constituents are converted into a clean burning fuel consisting primarily of CO, CO.sub.2 and H.sub.2 through a steam reforming reaction. Other constituents of the waste, which are able to withstand the high temperatures without becoming volatilized, are made to form into a molten state which then cools to form a stable glass. By carefully controlling the vitrification process, the resulting vitrified glass may be made to exhibit great stability against chemical and environmental attack, with a high resistance to leaching of the hazardous components bound up within the glass. In this manner, vitrification may be utilized to convert waste materials into a high quality fuel gas and a stable, environmentally benign, glass.
Because of the volatile nature of the clean burning fuels generated by the pyrolysis/steam reforming/vitrification process, it is desirable that the region wherein heating takes place and the fuel gasses are generated be kept separated from the ambient atmosphere. At the same time, as materials are vitrified, both the joule heating electrodes and the arc electrodes are consumed. Therefore, prior art processes have heated the waste materials in process chambers designed to keep the gaseous products of the process separate from the ambient atmosphere. Electrodes are introduced through penetrations in the process chamber. When the electrodes are consumed, the process is halted to allow the electrodes to be replaced. Stopping the vitrification process is undesirable because it lowers the processing throughput and may allow the processing chamber to cool which can cause damage or degradation to the process chamber. These and other drawbacks of the prior art have created a need for improved apparatus allowing the introduction of electrodes into a process chamber while maintaining the atmosphere within the process chamber as separate from the atmosphere exterior to the process chamber.